The present invention relates to the field of article stacking devices, and more particularly to stacking devices for assembling a stream of printed products into stacks and ejecting the stacks of printed products.
Newspapers and other printed matter which is ejected from a printing press or inserting machine is generally folded and delivered in a continuous stream with the papers in an overlapped relationship. The papers from the printing press are received and stacked by a stacking apparatus which must operate at very high speeds. The stacking apparatus generally forms the papers into stacks and ejects the stacks of papers in two directions from the stacker at a rate which exceeds one stack ejected per second.
The known stacking apparatuses generally operate by moving a fork into the continuous stream of papers to collect a desired number of papers which form a batch. The forks are generally spring mounted to a chain drive which rotates to continually receive and deliver batches of papers. After a predetermined count of papers are received on a fork, a next fork intercepts the paper stream and begins collecting papers for a next batch. The forks move downward as the papers are collected and drop the completed batches onto a turntable which collects the papers in a stack.
Since newspapers and other printed materials generally have a thickness which is greater along the folded side or sides of the papers than on the unfolded sides of the papers, two or more batches are generally stacked on the turntable with the folded edges of the successive batches rotated 180.degree. with respect to one another to achieve a stack with an even height. In order to form an even stack with rotated batches, the stacking platform or turntable is driven by a heavy duty motor which rotates the turntable 180.degree. between dropping of successive batches by the forks.
Once a predetermined stack size is reached, the stack is ejected from the stacking machine by pushing the stack off of the turntable with a pusher bar. The pusher bar of known stackers extends vertically through the turntable by passing through a clearance gap provided between two halves of the turntable platform. The pusher bar is driven by a chain drive to push the stack from the turntable onto one of two conveyors which are arranged to receive the stacks in two directions which are 180.degree. from each other.
The known stacking apparatuses are generally designed to operate with newspapers or other flat articles which vary in size, shape, weight, and conformity, and are not dimensionally stable. Therefore, the turntables of stackers generally include adjustable side walls or guides on all four sides of the stack which align and stabilize the stack. The end guides provided on the opposite ends of the stack are mounted on springs so that these end guides will open to allow the stacks to be ejected.
One drawback of known stacking apparatuses is the fact that the stacks are ejected only in the two directions which are normal to the direction in which the stream of newspapers enters the stacker. Thus, for many printing setups, the stream of incoming papers must be turned 90.degree. before entering the stacker. Alternatively, the two streams of stacks exiting the stacker may have to be turned 90.degree.. This need to rotate either the stream of papers or the two streams of stacks for some plant setups adds to the complexity, expense, and space taken up by the entire line.